Power converting system

ABSTRACT

A power converting system that includes: a rectifier configured to convert an input voltage into a output voltage and including an output node that is coupled to floating ground; a radio frequency (RF) power amplifier coupled to the rectifier and configured to generate a load voltage based on an RF clock and the output voltage; a detector coupled to the RF power amplifier and configured to detect the load voltage of the RF power amplifier; an integrator coupled to the detector and configured to generate a direct current (DC) voltage based on the detected load voltage; and a controller coupled to the integrator and configured to, based on the DC voltage, generate a control signal to adjust one or more features of the RF power amplifier is disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a non-provisional of and claims priority to U.S.Provisional Patent Application No. 62/493,967, filed on Jul. 21, 2016,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This disclosure relates generally to electronics and more particularlyto a power converting system that converts an alternating current (AC)line voltage to radio frequency (RF) energy for one or more devices.

BACKGROUND

A traditional power converting system that generates RF power from an ACline voltage usually includes a full wave bridge rectifier. However, thefull wave bridge rectifier offers a poor power factor so that the fullwave bridge rectifier is not an effective power supply solution.

SUMMARY

To provide a 50 W to multi-kW source of RF power for use in appliancessuch as dryers, cooking appliances, industrial heaters, dialecticheaters, medical RF ablation systems, induction heaters, or radiotransmitters, a power converting system operates at frequencies between100 kHz and 100 MHz with emphasis on the ISM frequency bands at 13.56MHz, 27.12 MHz, or 40.68 MHz. The power converting system can include aphase shifter or a pulse width controller to control output of a RFpower amplifier that is used as a RF source for appliances. The RF poweramplifier is powered by a rectifier. In particular, the RF poweramplifier can be powered by a Valley Fill rectifier. The output of theRF amplifier is adjustable over at least a 10 dB range.

In general, one innovative aspect of the subject matter described inthis specification can be implemented in a power converting systemcomprising: a rectifier configured to convert an input voltage into aoutput voltage and including an output node that is coupled to floatingground; a radio frequency (RF) power amplifier coupled to the rectifierand configured to generate a load voltage based on an RF clock and theoutput voltage; a detector coupled to the RF power amplifier andconfigured to detect the load voltage of the RF power amplifier; anintegrator coupled to the detector and configured to generate a directcurrent (DC) voltage based on the detected load voltage; and acontroller coupled to the integrator and configured to, based on the DCvoltage, generate a control signal to adjust one or more features of theRF power amplifier.

The foregoing and other implementations can each optionally include oneor more of the following features, alone or in combination. Inparticular, one implementation includes all the following features incombination. The power converting system further includes: a referencevoltage generator configured to generate a reference voltage, whereinthe controller is configured to: compare the output signal to thereference voltage, based on the comparison of the output signal to thereference voltage, generate the control signal. The reference voltagerepresents a desired RF output power of the power converting system. Thepower converting system further includes: a coupler coupled to the RFpower amplifier and configured to transfer output of the RF poweramplifier to the detector. The coupler is a directional coupler that isconfigured to sense the output of the RF power amplifier delivered to aRF load. The load voltage of the RF power amplifier is provided to a RFload. The RF load includes one or more resistors. The power convertingsystem further includes: a RF clock generator coupled to the RF poweramplifier and configured to provide the RF clock to the RF poweramplifier. A frequency of the RF clock is an operating frequency of thepower converting system. The controller is configured to: based on theDC voltage, generate the control signal to adjust a phase of the RFclock. The RF power amplifier includes: a phase shifter configured to:receive the control signal from the controller, and based on the controlsignal, adjust the phase of the RF clock. The RF power amplifierincludes: a first switching unit that is configured to receive the RFclock, a second switching unit that is configured to receive the RFclock, a third switching unit that is configured to receive the RF clockthrough the phase shifter, and a fourth switching unit that isconfigured to receive the RF clock through the phase shifter, whereinthe phase shifter is configured to adjust the phase of the RF clock andprovide the phase adjusted RF clock to the third switching unit and thefourth switching unit. The second switching unit and the third switchingunit are coupled to floating ground. The RF power amplifier furtherincludes: a resonant circuit having a first resonant frequency, andwherein an operating frequency of the RF power amplifier is the same asthe first resonant frequency. The operating frequency of the RF poweramplifier is between 100 kHz and 100 MHz. The RF power amplifierincludes: a fifth switching unit that is configured to receive the RFclock, and a sixth switching unit that is configured to receive the RFclock, and wherein the phase shifter is configured to adjust the phaseof the RF clock and provide the phase adjusted RF clock to the fifthswitching unit and the sixth switching unit. The fifth switching unitand the sixth switching unit are coupled to floating ground. The RFpower amplifier further includes: a resonant circuit having a firstresonant frequency, and wherein an operating frequency of the RF poweramplifier is the same as the first resonant frequency. The operatingfrequency of the RF power amplifier is between 100 kHz and 100 MHz. Thecontroller is configured to: based on the DC voltage, generate thecontrol signal to adjust a pulse width of the RF clock. The RF poweramplifier includes: a pulse width controller that is configured to:receive the control signal from the controller, and based on the controlsignal, adjust the pulse width of the RF clock. The RF power amplifierincludes: a first switching unit that is configured to receive the RFclock through the pulse width controller, a second switching unit thatis configured to receive the RF clock through the pulse widthcontroller, a third switching unit that is configured to receive the RFclock through the pulse width controller, and a fourth switching unitthat is configured to receive the RF clock through the pulse widthcontroller, wherein the pulse width controller is configured to adjustthe pulse width of the RF clock and provide the pulse width-adjusted RFclock to the first switching unit, the second switching unit, the thirdswitching unit, and the fourth switching unit. The second switching unitand the third switching unit are coupled to floating ground. The RFpower amplifier further includes: a resonant circuit having a firstresonant frequency, and wherein an operating frequency of the RF poweramplifier is the same as the first resonant frequency. The operatingfrequency of the RF power amplifier is between 100 kHz and 100 MHz. TheRF power amplifier includes: a fifth switching unit that is configuredto receive the RF clock, and a sixth switching unit that is configuredto receive the RF clock, and wherein the pulse width controller isconfigured to adjust the pulse width of the RF clock and provide thepulse width-adjusted RF clock to the fifth switching unit and the sixthswitching unit. The fifth switching unit and the sixth switching unitare coupled to floating ground. The RF power amplifier further includes:a resonant circuit having a first resonant frequency, and wherein anoperating frequency of the RF power amplifier is the same as the firstresonant frequency. The operating frequency of the RF power amplifier isbetween 100 kHz and 100 MHz. The rectifier is a Valley Fill rectifier.An operating frequency of the RF power amplifier is between 13 and 14MHz.

The subject matter described in this specification can be implemented inparticular implementations so as to realize one or more of the followingadvantages. Comparing to a conventional power converting system, thepower converting system described above maximizes AC line to RF poweroutput conversion efficiency. The power converting system also maximizesAC input power factor (PF) so that the RF power amplifier can delivermaximum RF output power within the ratings of standard AC line currentprotection devices and meet international standards for appliance powerfactor. Moreover, the RF power amplifier is designed to minimize heatingof a RF power metal-oxide-semiconductor field-effect transistor (MOSFET)or other switching devices used when the power supply is delivering peakoutput voltage such that the life of the RF power MOSFET and theswitching devices can be maximized. Furthermore, the power convertingsystem provides a cost-effective solution.

The details of one or more disclosed implementations are set forth inthe accompanying drawings and the description below. Other features,aspects, and advantages will become apparent from the description, thedrawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram illustrating an example power converting system.

FIG. 1B is a diagram illustrating another example power convertingsystem.

FIG. 2A is a diagram illustrating an example RF power amplifierincluding a phase shifter 127.

FIG. 2B is a diagram illustrating another example RF power amplifierincluding a phase shifter.

FIG. 2C is a diagram illustrating an example timing chart showingvoltage levels at gates of transistors and a voltage across atransformer in FIG. 2B.

FIG. 3A is a diagram illustrating an example RF power amplifierincluding a pulse width controller.

FIG. 3B is a diagram illustrating another example RF power amplifierincluding a pulse width controller.

FIG. 3C is a diagram illustrating an example timing chart showingvoltage levels at gates of transistors and a voltage across atransformer in FIG. 3B.

FIG. 4A is a diagram illustrating another example RF power amplifierincluding a phase shifter.

FIG. 4B is a diagram illustrating another example RF power amplifierincluding a phase shifter.

FIG. 5A is a diagram illustrating another example RF power amplifierincluding a pulse width controller.

FIG. 5B is a diagram illustrating another example RF power amplifierincluding a pulse width controller.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1A illustrates an example power converting system 100. The powerconverting system 100 includes a rectifier 110, a RF clock generator112, a radio frequency (RF) power amplifier 120, a coupler 130, adetector 140, a RF load 150, a reference voltage generator 160, and thecontroller 170. The power converting system 100 may be implemented withan integrated circuit or with a combination of integrated circuitsand/or individual discrete components. The power converting system 100can be included in various electronic systems, including but not limitedto: dryers, cooking appliances, industrial heaters, dialectic heaters,medical RF ablation systems, induction heaters, or radio transmitters.

The rectifier 110 converts an input voltage (Vin) into an output voltage(Vout). Input of the rectifier 110 is coupled to an AC power line havinga particular frequency, e.g., 60 Hz. In some implementations, therectifier 110 can be a single-phase rectifier or a multi-phaserectifier, such as a three-phase rectifier. In some implementations, therectifier 110 can be a full wave bridge rectifier. A full wave bridgerectifier provides excellent power efficiency. In some otherimplementations, the rectifier 110 can be a Valley Fill rectifier. AValley Fill rectifier improves power factor and power efficiency. Inaddition, a Valley Fill rectifier is cost-effective.

In some implementations, a transformer operating at the AC power linefrequency is not required for the rectifier 110. Thus, the rectifier 110is not isolated from the AC power line. In some implementations, toprevent a safety hazard, elements of the rectifier 110 and elementsfollowing output of the rectifier 110 are coupled to floating groundrather than chassis ground. For example, floating ground can be a commonnode that other voltages in the power converting system 100 arereferenced to but is not tied to chassis or earth ground.

During operation of the RF power amplifier 120, the RF clock generator112 provides an RF clock to the RF power amplifier 120. The RF clockgenerator 112 is coupled to floating ground. An RF output frequency ofthe power converting system 100 is determined by the frequency of the RFclock.

The RF power amplifier 120 is coupled to the output of the rectifier110. The output of the rectifier 110 is coupled to an input of the RFpower amplifier 120. The ground in the RF power amplifier 120 isisolated from chassis ground. One or more circuit elements requiring aconnection to ground in the RF power amplifier 120 are coupled tofloating ground. The RF power amplifier 120 is driven by the RF clock.In some implementations, the RF power amplifier 120 can be a class D,class DE, class E, or class F RF power amplifiers with varioustopologies. For example, a push pull and full bridge topology offerspecial advantages for RF power amplifiers requiring control of RFoutput power. The RF power amplifier 120 provides power to the RF load150 through the coupler 130. The load voltage (V_(L)) across the RF load150 can be the output voltage of the power converting system 100. Insome implementations, the RF load 150 can include one or moreresistances. In some implementations, RF power amplifier 120 includes atransformer. Where the RF power amplifier 120 includes a transformer,the RF load 150 is isolated from the input of the RF power amplifier120. Thus, the RF load 150 may be coupled to chassis ground.

The coupler 130 also transfers the output of the RF power amplifier 120to the detector 140. In some implementations, the coupler 130 can be adirectional coupler. That is, the coupler 130 detects RF signals flowingin one direction, e.g., a direction from the RF power amplifier 120 tothe RF load 150.

The detector 140 is coupled to the output of the coupler 130. Thedetector 140 detects the output voltage of the RF power amplifier 120and generates an output signal (OutputSignal). The detector 140 providesthe output signal (OutputSignal) to the integrator 180. The integrator180 converts the output signal (OutputSignal), which may be a complexwaveform, to a DC voltage. The integrator 180 provides the converted DCvoltage to the controller 170.

The reference voltage generator 160 generates a reference voltage (Vref)and provides the reference voltage (Vref) to the controller 170. Thereference voltage (Vref) represents the desired output power level ofthe power converting system 100.

The controller 170 receives, as input, the DC voltage from theintegrator 180 and the reference voltage (Vref) from the referencevoltage generator 160. The controller 170 compares the DC voltage to thereference voltage (Vref). Based on the comparison of the DC voltage tothe reference voltage (Vref), the controller 170 generates a controlsignal to control the RF power output of the power converting system100. For example, the controller 170 can calculate the differencebetween the DC voltage and the reference voltage (Vref). The controller170 determines whether the difference satisfies a threshold, e.g., thedifference is above the threshold or below the threshold. Based on adetermination that the difference satisfies the threshold, thecontroller 170 can generate a control signal to control the RF poweroutput of the power converting system 100.

The control signal generated by the controller 170 adjusts one or morefeatures of the RF power amplifier 120 to control the RF power output ofthe power converting system 100. In some implementations, the controlsignal generated by the controller 170 can adjust the phase of the RFclock within the RF power amplifier 120 to control the load voltage(V_(L)). In some other implementations, the control signal generated bythe controller 170 can adjust a pulse width of the RF clock within theRF power amplifier 120 to control the load voltage (V_(L)). Bycontrolling the load voltage (V_(L)), the power converting system 100can reduce power consumption of the power converting system 100.

FIG. 1B illustrates another example power converting system 100. In FIG.1B, the integrator 180 includes a capacitor C0, a resistor R0, and an opamp OP. The resistor R0 is coupled between the node N3 and the node N4and the capacitor C0 is coupled between the node N4 and the node N5. Thenode N3 is coupled to the output of detector 140, the node N4 is coupledto a first inverting input terminal of the op amp OP. A secondnon-inverting input terminal of the op amp OP is coupled to floatingground. The integrator 180 converts the output signal (OutputSignal)from the detector 140 to a DC voltage. The converted DC voltage isprovided to the controller 170. The operation of the controller 170 isthe same as the controller 170 illustrated in FIG. 1A.

FIG. 2A illustrates an example RF power amplifier 120 including a phaseshifter 127. In some implementations, the phase shifter 127 can be ananalog phase shifter. In some other implementations, the phase shifter127 can be a digital phase shifter. The RF power amplifier 120 includesa first switching unit 121, a second switching unit 122, a thirdswitching unit 123, a fourth switching unit 124, a transformer 125, aresonator 126, and a phase shifter 127. The switching units 121-124 canbe implemented with a various kinds of transistors including, but notlimited to: P-channel MOSFETs, N-channel MOSFETs, LDMOS transistors,Silicon MOSFETs, Silicon Carbide MOSFETs, Silicon Bipolar Transistors,Silicon IGBTs, Silicon JFETs, Silicon Carbide JFETs, Gallium NitrideHigh Electron Mobility Transistors (GaN HEMTs), GaAs MESFETs, or anysuitable types of transistors.

In some implementations, the switching units 121-124 can be respectivelydriven by a suitable high current driver D1-D4 to charge or dischargeinput capacitance of the switching units 121-124. For example, asuitable high current driver can charge the input capacitance within 5%of the RF signal's period. The high current driver can be controlled bytransistor-transistor logic (TTL) or CMOS signals. As a result, thepower converting system 100 can have a simple interface to digital oranalog control the phase shifter 127 or pulse width controller 128.

In some implementations, the switching units 121-124 are the same typeof transistors. For example, the switching units 121-124 are N-channelSilicon MOSFETs. In these implementations, the RF power amplifier 120can include inverters for the second switching unit 122 and the fourthswitching unit 124. Alternatively, the RF power amplifier 120 caninclude inverters for the first switching unit 121 and the thirdswitching unit 123. In some other implementations, the first switchingunit 121 and the third switching unit 123 are the same type oftransistors and the second switching unit 122 and the fourth switchingunit 124 are the same type of transistors. For example, the firstswitching unit 121 and the third switching unit 123 are N-channelSilicon MOSFETs and the second switching unit 122 and the fourthswitching unit 124 are P-channel Silicon MOSFETs. In theseimplementations, the RF power amplifier 120 does not include inverters.The operations of the switching units 121-124 are described in greaterdetail below

The first switching unit 121 is coupled between the node N1 and a nodeN9. The first switching unit 121 is turned on or off in response to theRF clock. For example, when the RF clock is high, the first switchingunit 121 is turned on. When the RF clock is low, the first switchingunit 121 is turned off. In some implementations, the RF power amplifier120 additionally includes a driver D1 that is coupled between the nodeN10 and the first switching unit 121 to drive the first switching unit121.

The second switching unit 122 is coupled between the node N9 and thenode N2. The second switching unit 122 is turned on or off in responseto the RF clock. For example, when the RF clock is high, the secondswitching unit 122 is turned off. When the RF clock is low, the secondswitching unit 122 is turned on. In some implementations, the RF poweramplifier 120 can include an inverter IN1 between the node N10 and thesecond switching unit 122. In these implementations, the first switchingunit 121 and the second switching unit 122 are the same type oftransistors. In some implementations, the second switching unit 122 canbe a different type of transistor from the first switching unit 121. Forexample, if the first switching unit 121 is a P-channel Silicon MOSFET,the second switching unit 122 is an N-channel Silicon MOSFET. In theseimplementations, the RF power amplifier 120 does not include aninverter. In some implementations, the RF power amplifier 120additionally includes a driver D2 between the node N10 and the secondswitching unit 122 to drive the second switching unit 122.

The third switching unit 123 is coupled between the node N2 and a nodeN11. The third switching unit 123 is turned on or off in response to theRF clock. For example, where the phase of the RF clock is not shifted bythe phase shifter 127, when the RF clock is high, the third switchingunit 123 is turned on. When the RF clock is low, the third switchingunit 123 is turned off. As another example, where the phase of the RFclock is shifted by the phase shifter 127, when the RF clock is high,the third switching unit 123 can be turned on or off based on how muchthe phase of the RF clock is shifted. When the RF clock is low, thethird switching unit 123 can be turned on or off based on how much thephase of the RF clock is shifted. In some implementations, the RF poweramplifier 120 additionally includes a driver D3 that is coupled betweenthe phase shifter 127 and the third switching unit 123 to drive thethird switching unit 123.

The fourth switching unit 124 is coupled between the node N11 and thenode N1. The fourth switching unit 124 is turned on or off in responseto the RF clock. For example, where the phase of the RF clock is notshifted by the phase shifter 127, when the RF clock is high, the fourthswitching unit 124 is turned off. When the RF clock is low, the fourthswitching unit 124 is turned on. As another example, where the phase ofthe RF clock is shifted by the phase shifter 127, when the RF clock ishigh, the fourth switching unit 124 can be turned on or off based on howmuch the phase of the RF clock is shifted. When the RF clock is low, thefourth switching unit 124 can be turned on or off based on how much thephase of the RF clock is shifted. In some implementations, the RF poweramplifier 120 can include an inverter IN2 between the phase shifter 127and the fourth switching unit 124. In these implementations, the thirdswitching unit 123 and the fourth switching unit 124 are the same typeof transistors. In some other implementations, the fourth switching unit124 can be a different type of transistor from the third switching unit123. For example, if the third switching unit 123 is a P-channel SiliconMOSFET, the fourth switching unit 124 can be an N-channel SiliconMOSFET. In these implementations, the RF power amplifier 120 does notinclude an inverter. In some implementations, the RF power amplifier 120additionally includes a driver D4 between the phase shifter 127 and thefourth switching unit 124 to drive the fourth switching unit 124.

The transformer 125 is coupled between the node N9 and the node N11. Thetransformer 125 includes a primary and a secondary. Since the primary isseparated from the secondary, the transformer 125 isolates the RF load150 from the RF power amplifier 120 of the power converting system 100.In some implementations, the secondary of the transformer 125, theresonator 126, and the RF load 150 can be coupled to chassis ground. Insome implementations, where the rectifier 110 is a Valley Fillrectifier, the switching units 121-124 dissipate maximum power when therectifier 110 delivers peak output voltage and the RF power output ofthe power converting system 100 is the maximum.

The transformer 125 delivers RF power from the primary to the secondary.The secondary of the transformer 125 is coupled to the resonator 126.The resonator 126 is coupled to chassis ground. The power transferredfrom the primary to the secondary is transferred to the resonator 126and the RF load 150. Where the resonant frequency of the resonator 126is the same as the operating frequency of the RF power amplifier 120,the resonator 126 has low impedance, e.g., less than 1 ohm. Thus, nearlyall the power transferred from the primary to the secondary istransferred to the RF load 150.

The phase shifter 127 couples the node N10 to both of the thirdswitching unit 123 and the fourth switching unit 124. In response to thecontrol signal received from the controller 170, the phase shifter 127adjusts the phase of the RF clock and provides the phase-adjusted RFclock to both of the third switching unit 123 and the fourth switchingunit 124 such that the output power of the RF power amplifier 120 issmoothly adjusted from zero to the maximum. Adjusting output power ofthe RF power amplifier 120 will be described in greater detail withreference to the FIG. 2C.

FIG. 2B illustrates another example RF power amplifier 100 including aphase shifter 127. In this example, the switching units 121-124 areimplemented using N-channel Silicon MOSFETs T1-T4. Each of the switchingunits 121-124 can additionally include any suitable circuit elements. Insome implementations, the switching units 121-124 can be implementedusing different types of transistors or other circuit elements.

With reference to FIG. 2B, a drain of the transistor T1 is coupled tothe node N1, a gate of the transistor T1 is coupled to a node 12, and asource of the transistor T1 is coupled to the node N9. In response tothe RF clock, the transistor T1 is turned on or off. When the RF clockis high, the transistor T1 is turned on. When the RF clock is low, thetransistor T1 is turned off.

A drain of the transistor T2 is coupled to the node N9, a gate of thetransistor T2 is coupled to a node 13, and a source of the transistor T2is coupled to the node N2. The RF clock is inverted by the inverter IN1,driven by the driver D1, and then, provided to the gate of thetransistor T2 to turn on or off the transistor T2. When the RF clock ishigh, the transistor T2 is turned off. When the RF clock is low, thetransistor T2 is turned on.

A drain of the transistor T3 is coupled to the node N11, a gate of thetransistor T3 is coupled to a node N14, and a source of the transistorT3 is coupled to the node N2. In response to the RF clock that is drivenby the driver D3, the transistor T3 is turned on or off. When the RFclock is high, the transistor T3 is turned on. When the RF clock is low,the transistor T3 is turned off.

A drain of the transistor T4 is coupled to the node N1, a gate of thetransistor T4 is coupled to a node 15, and a source of the transistor T4is coupled to the node N11. The RF clock is inverted by the inverterIN2, driven by the driver D4, and then, provided to the gate of thetransistor T4 to turn on or off the transistor T4. When the RF clock ishigh, the transistor T4 is turned off. When the RF clock is low, thetransistor T4 is turned on.

The transformer 125 includes a primary L1 and a secondary L2 to deliverthe voltage (V_(L1)) between the node N9 and the node N11 into the loadvoltage (V_(L)). The transformer 125 includes two isolated coils L1, L2.These coils L1, L2 of the transformer 125 isolate the RF load 150 fromthe RF power amplifier 120 of the power converting system 100 asdescribed above. The resonator 126 includes a resonant circuit includingan inductor L 1 and a capacitor C1. The RF load 150 is coupled to theresonator 126. In some implementations, the inductor L1 and thecapacitor C1 have any suitable values of inductance and capacitance suchthat the resonant circuit of the resonator 126 has a resonant frequencythat is the same as the operating frequency of the RF power amplifier120 as determined by RF clock. For example, the resonant frequency ofthe resonator 126 and the operating frequency of the RF power amplifier120 can be 13.56 MHz. Where the resonant frequency is the same as theoperating frequency of the RF power amplifier 120, the resonator 126 haslow impedance, e.g., less than 1 ohm, and nearly all the power from thesecondary of the transformer is delivered to the RF load 150. In someimplementations, the coupler 130 described with reference to FIGS. 1Aand 1B can be coupled between the resonator 126 and the RF load 150.

The phase shifter 127 is coupled between the node N10 and both of thenode N14 and the node N15. In response to the control signal receivedfrom the controller 170, the phase shifter 127 adjusts the phase of theRF clock and provides the phase-adjusted RF clock to both of the gate ofthe transistor T3 and the gate of the transistor T4 such that the outputpower of the RF power amplifier 120 is smoothly adjusted from zero tothe maximum.

FIG. 2C illustrates an example timing chart showing voltage levels atthe gates of the transistors T1-T4 and the voltage (V_(L1)) in FIG. 2B.Referring to FIG. 2B, the node 12 is coupled to the gate of thetransistor T1, the node 13 is coupled to the gate of the transistor T2,the node N14 is coupled to the gate of the transistor T3, and the node15 is coupled to the gate of the transistor T4. When the phase is notshifted, i.e., 0 degree phase shift, the voltage (V_(L1)) that is avoltage across the primary L1 of the transformer 125 is transitioned atthe same timing that the RF clock is transitioned. When the phaseshifter 127 shifts the phase of the RF clock by 90 degrees, the voltagesat the nodes N12, N13 are not shifted, but the voltages at the nodesN14, N15 are shifted by 90 degrees. As a result, the RMS voltage(V_(L1)) is reduced comparing to the RMS voltage (V_(L1)) with 0 degreephase shift. When the phase shifter 127 shifts the phase of the RF clockby 180 degrees, the voltages at the nodes N12, N13 are not shifted, butthe voltages at the nodes N14, N15 are shifted by 180 degrees. As aresult, the voltage (V_(L1)) has zero output. Thus, by adjusting thephase of the RF clock, the RF power amplifier 120 can reduce the output,which is the voltage (V_(L1)), of the RF power amplifier 120 such thatthe output of the RF power amplifier 120 is smoothly adjusted from zeroto the maximum. The current flowing in the secondary L2 of thetransformer 125 is filtered by the resonator 126, which can only passthe RF clock frequency. Thus, the load voltage (V_(L)) across the RFload 150 becomes a sign wave.

FIG. 3A illustrates an example RF power amplifier including a pulsewidth controller. The RF power amplifier 120 can include the sameelements described with reference to FIG. 2A except the phase shifter127. Instead of the phase shifter 127, the RF power amplifier 120 inFIG. 3A includes a pulse width controller 128. The pulse widthcontroller 128 controls a pulse width of the RF clock. In someimplementations, the pulse width controller 128 can be an analog pulsewidth controller. In some other implementations, the pulse widthcontroller 128 can be a digital pulse width controller. Where the phaseshifter 127 in FIG. 2A is coupled to the third switching unit 123 andthe fourth switching unit 124, but not coupled to the first switchingunit 121 and the second switching unit 122, the pulse width controller128 in FIG. 3A is coupled to all of the switching units 121-124. Thepulse width controller 128 receives the RF clock as input and provides apulse width-adjusted RF clock to the node N10. In particular, inresponse to the control signal received from the controller 170, thepulse width controller 128 adjusts the pulse width of the RF clock andprovides the pulse width-adjusted RF clock to all of the switching units121-124 such that the output power of the RF power amplifier 120 issmoothly adjusted from zero to the maximum based on the adjustment ofthe pulse width. The power output adjustment achieved by adjusting thepulse width of the RF clock will be described in greater detail withreference to the FIG. 3C.

FIG. 3B illustrates another example RF power amplifier including a pulsewidth controller. In this example, the switching units 121-124 areimplemented using N-channel Silicon MOSFETs T1-T4. Each of the switchingunits 121-124 can additionally include any suitable circuit elements. Insome implementations, the switching units 121-124 can be implementedusing different types of transistors or other circuit elements.

The RF power amplifier 120 can include the same elements described withreference to FIG. 2B except the phase shifter 127. Instead of the phaseshifter 127, the RF power amplifier 120 in FIG. 3B includes the pulsewidth controller 128. Where the phase shifter 127 in FIG. 2B is coupledto the gate of the transistor T3 and the gate of the transistor T4, butnot coupled to the gate of the transistor T1 and the gate of thetransistor T2, the pulse width controller 128 is respectively coupled toall of the gates of the transistors T1-T4. The pulse width controller128 receives the RF clock as input and provides a pulse width-adjustedRF clock to the node N10. In particular, in response to the controlsignal received from the controller 170, the pulse width controller 128adjusts the pulse width of the RF clock and provides the pulsewidth-adjusted RF clock to all of the transistors T1-T4 such that theoutput power of the RF power amplifier 120 is smoothly adjusted fromzero to the maximum. The output power adjustment achieved by the pulsewidth of the RF clock will be described in greater detail with referenceto the FIG. 3C.

FIG. 3C illustrates an example timing chart showing voltage levels atthe gates of the transistors T1-T4 and the voltage (V_(L1)) in FIG. 3B.Referring to FIG. 3B, the node 12 is coupled to the gate of thetransistor T1, the node 13 is coupled to the gate of the transistor T2,the node N14 is coupled to the gate of the transistor T3, and the node15 is coupled to the gate of the transistor T4. When the pulse width ofthe RF clock is not adjusted, the voltage (V_(L1)) that is a voltageacross the primary L1 of the transformer 125 is transitioned at the sametiming that the RF clock is transitioned. When the pulse widthcontroller 128 adjusts, i.e., reduces, the pulse width of the RF clockby 50%, the voltages at the nodes N12-N15 are respectively adjusted. Asa result, the voltage (V_(L1)) is reduced by 50% comparing to thevoltage (V_(L1)) when a pulse width of the RF clock is not adjusted.When the pulse width controller 128 adjusts, i.e., reduces, the pulsewidth of the RF clock to zero, the voltage (V_(L1)) has zero output.Thus, by adjusting the pulse width of the RF clock, the RF poweramplifier 120 can reduce the output of the RF power amplifier 120, whichis the voltage (V_(L1)), such that the output power of the RF poweramplifier 120 is smoothly adjusted from zero to the maximum.

FIG. 4A illustrates an example RF power amplifier including a phaseshifter. The RF power amplifier 120 can include the same elementsdescribed with reference to FIG. 2A except that the RF power amplifier120 includes two switching units, i.e., a fifth switching unit 221 andsixth switching unit 222 instead of the switching units 121-124. Theswitching units 221, 222 can be implemented with a various kinds oftransistors including, but not limited to: P-channel MOSFETs, N-channelMOSFETs, LDMOS transistors, Silicon MOSFETs, Silicon Carbide MOSFETs,Silicon Bipolar Transistors, Silicon IGBTs, Silicon JFETs, SiliconCarbide JFETs, Gallium Nitride High Electron Mobility Transistors (GaNHEMTs), GaAs MESFETs, or any suitable types of transistors. In someimplementations, the switching units 221, 222 are the same type oftransistors. For example, the switching units 221, 222 are N-channelSilicon MOSFETs. In these implementations, the RF power amplifier 120can include an inverter for the fifth switching unit 221. Alternatively,the RF power amplifier 120 can include an inverter for the sixthswitching unit 222. In some other implementations, the fifth switchingunit 221 is a different type of transistor from the sixth switching unit222. For example, the fifth switching unit 221 includes a P-channelSilicon MOSFET and the sixth switching unit 222 includes a N-channelSilicon MOSFET. In these implementations, the RF power amplifier 120does not include inverters. The details of the switching units 221-222are described in greater detail below.

The fifth switching unit 221 is coupled between the node N9 and the nodeN2. The fifth switching unit 221 is turned on or off in response to theRF clock. For example, when the RF clock is high, the fifth switchingunit 221 is turned off. When the RF clock is low, the fifth switchingunit 221 is turned on. In some implementations, the RF power amplifier120 can include an inverter IN3 between the node N10 and the fifthswitching unit 221. In these implementations, the fifth switching unit221 and the sixth switching unit 222 are the same type of transistors.In some implementations, the sixth switching unit 222 can be a differenttype of transistor from the fifth switching unit 221. For example, wherethe fifth switching unit 221 is a N-channel Silicon MOSFET, the sixthswitching unit 222 is a P-channel Silicon MOSFET. In theseimplementations, the RF power amplifier 120 does not include theinverter IN3. In some implementations, the RF power amplifier 120additionally includes a driver D5 between the node N10 and the fifthswitching unit 221 to drive the fifth switching unit 221.

The sixth switching unit 222 is coupled between the node N2 and a nodeN11. The sixth switching unit 222 is turned on or off in response to theRF clock. For example, when the RF clock is high, the sixth switchingunit 222 is turned on. When the RF clock is low, the sixth switchingunit 222 is turned off. In some implementations, the RF power amplifier120 additionally includes a driver D6 that is coupled between the phaseshifter 127 and the sixth switching unit 222 to drive the sixthswitching unit 222.

The transformer 125 is coupled between the node N9 and the node N11. Thetransformer 125 includes a primary coupled between the node N9 and thenode N11 and a secondary coupled to the resonator 126. The RF load 150is coupled to the resonator 126. The node N1 is coupled to a portion ofthe transformer 125. In particular, the node N1 can be coupled to thecenter of the primary coil of the transformer 125. The transformer 125delivers power from the primary to the secondary and the transferredpower to the secondary is transferred to the resonator 126 and the RFload 150. In this example, the resonator 126 is coupled to chassisground. Where the resonant frequency of the resonator 126 is the same asthe operating frequency of the RF power amplifier 120, the resonator 126has low impedance, e.g., less than 1 ohm. Thus, nearly all the powertransferred from the primary to the secondary is transferred to the RFload 150.

The phase shifter 127 couples the node N10 to the sixth switching unit222. In response to the control signal received from the controller 170,the phase shifter 127 adjusts the phase of the RF clock and provides thephase-adjusted RF clock to both of the fifth switching unit 221 and thesixth switching unit 222 such that the output power of the RF poweramplifier 120 is smoothly adjusted from zero to the maximum based on theadjustment of the phase.

FIG. 4B illustrates another example RF power amplifier including a phaseshifter. In this example, the switching units 221, 222 are implementedusing N-channel Silicon MOSFETs T5, T6. Each of the switching units 221,222 can additionally include any suitable circuit elements. In someimplementations, the switching units 221, 222 can be implemented usingdifferent types of transistors or other circuit elements.

With reference to FIG. 4B, a drain of the transistor T5 is coupled tothe node N9, a gate of the transistor T2 is coupled to the node 13, anda source of the transistor T2 is coupled to the node N2. The RF clock isinverted by the inverter IN3, driven by the driver D5, and then,provided to the gate of the transistor T5 to turn on or off thetransistor T5. For example, when the RF clock is high, the transistor T5is turned off. When the RF clock is low, the transistor T5 is turned on.

A drain of the transistor T6 is coupled to the node N11, a gate of thetransistor T6 is coupled to a node N14, and a source of the transistorT6 is coupled to the node N2. In response to the RF clock that is drivenby the driver D6, the transistor T6 is turned on or off. For example,where the phase of the RF clock is not shifted by the phase shifter 127,when the RF clock is high, the transistor T6 is turned on. When the RFclock is low, the transistor T6 is turned off. As another example, wherethe phase of the RF clock is shifted by the phase shifter 127, when theRF clock is high, the transistor T6 can be turned on or off based on howmuch the phase of the RF clock is shifted. When the RF clock is low, thetransistor T6 can be turned on or off based on how much the phase of theRF clock is shifted.

The transformer 125 includes a primary L1 and a secondary L2 to deliverthe voltage (V_(L1)) between the node N9 and the node N11 into the loadvoltage (V_(L)). The transformer 125 includes two isolated coils L1, L2.These coils L1, L2 of the transformer 125 isolate the RF load 150 fromthe RF power amplifier 120 of the power converting system 100 asdescribed above. The resonator 126 includes a resonant circuit includingan inductor L 1 and a capacitor C1. The RF load 150 is coupled to theresonator 126. In some implementations, the inductor L1 and thecapacitor C1 have any suitable values of inductance and capacitance suchthat the resonant circuit of the resonator 126 has a resonant frequencythat is the same as the operating frequency of the RF power amplifier120. For example, the resonant frequency of the resonator 126 and theoperating frequency of the RF power amplifier 120 can be 13.56 MHz.Where the resonant frequency is the same as the operating frequency ofthe RF power amplifier 120, the resonator 126 has low impedance, e.g.,less than 1 ohm, and nearly all the power from the secondary of thetransformer is delivered to the RF load 150. In some implementations,the coupler 130 described with reference to FIGS. 1A and 1B can becoupled between the resonator 126 and the RF load 150.

The phase shifter 127 is coupled between the node N10 and the node N14.In response to the control signal received from the controller 170, thephase shifter 127 adjusts the phase of the RF clock and provides thephase-adjusted RF clock to both of the gate of the transistor T5 and thegate of the transistor T6 such that the output power of the RF poweramplifier 120 is smoothly adjusted from zero to maximum.

FIG. 5A illustrates an example RF power amplifier including a pulsewidth controller. The RF power amplifier 120 can include the sameelements described with reference to FIG. 4A except the phase shifter127. Instead of the phase shifter 127, the RF power amplifier 120 inFIG. 5A includes the pulse width controller 128. The pulse widthcontroller 128 can be a pulse width controller described with referenceto FIG. 3A. The pulse width controller 128 in FIG. 5A is coupled to bothof the fifth switching unit 221 and the sixth switching unit 222. Thepulse width controller 128 receives the RF clock as input and provides apulse width-adjusted RF clock at the node N10. In particular, inresponse to the control signal received from the controller 170, thepulse width controller 128 adjusts the pulse width of the RF clock andprovides the pulse width-adjusted RF clock to all of the switching units221, 222 such that the output power of the RF power amplifier 120 issmoothly adjusted from zero to maximum based on the adjustment of thepulse width.

FIG. 5B illustrates another example RF power amplifier including a pulsewidth controller. In this example, the switching units 221, 222 areimplemented using N-channel Silicon MOSFETs T5, T6. Each of theswitching units 221, 222 can additionally include any suitable circuitelements. In some implementations, the switching units 221, 222 can beimplemented using different types of transistors or other circuitelements.

The RF power amplifier 120 can include the same elements described withreference to FIG. 4B except the phase shifter 127. Instead of the phaseshifter 127, the RF power amplifier 120 in FIG. 5B includes the pulsewidth controller 128. The pulse width controller 128 is respectivelycoupled to all of the gates of the transistors T5, T6. The pulse widthcontroller 128 receives the RF clock as input and provides a pulsewidth-adjusted RF clock at the node N10. In particular, in response tothe control signal received from the controller 170, the pulse widthcontroller 128 adjusts the pulse width of the RF clock and provides thepulse width-adjusted RF clock to all of the transistors T5, T6 such thatthe output of the RF power amplifier 120 is smoothly adjusted from zeroto the maximum based on the adjustment of the pulse width.

While this document contains many specific implementation details, theseshould not be construed as limitations on the scope what may be claimed,but rather as descriptions of features that may be specific toparticular implementations. Certain features that are described in thisspecification in the context of separate implementations can also beimplemented in combination in a single implementation. Conversely,various features that are described in the context of a singleimplementation can also be implemented in multiple implementationsseparately or in any suitable sub combination. Moreover, althoughfeatures may be described above as acting in certain combinations andeven initially claimed as such, one or more features from a claimedcombination can, in some cases, be excised from the combination, and theclaimed combination may be directed to a sub combination or variation ofa sub combination.

What is claimed is:
 1. A power converting system comprising: a rectifierconfigured to convert an input voltage into a output voltage andincluding an output node that is coupled to floating ground; a radiofrequency (RF) power amplifier coupled to the rectifier and configuredto generate a load voltage based on an RF clock and the output voltage;a detector coupled to the RF power amplifier and configured to detectthe load voltage of the RF power amplifier; an integrator coupled to thedetector and configured to generate a direct current (DC) voltage basedon the detected load voltage; and a controller coupled to the integratorand configured to, based on the DC voltage, generate a control signal toadjust one or more features of the RF power amplifier.
 2. The powerconverting system of claim 1, further comprising: a reference voltagegenerator configured to generate a reference voltage, wherein thecontroller is configured to: compare the DC voltage to the referencevoltage, based on the comparison of the DC voltage to the referencevoltage, generate the control signal.
 3. The power converting system ofclaim 1, wherein the reference voltage represents a desired RF outputpower of the power converting system.
 4. The power converting system ofclaim 1, further comprising: a coupler coupled to the RF power amplifierand configured to transfer output of the RF power amplifier to thedetector.
 5. The power converting system of claim 4, wherein the coupleris a directional coupler that is configured to sense the output of theRF power amplifier delivered to a RF load.
 6. The power convertingsystem of claim 1, wherein the load voltage of the RF power amplifier isprovided to a RF load.
 7. The power converting system of claim 6,wherein the RF load includes one or more resistors.
 8. The powerconverting system of claim 1, further comprising: a RF clock generatorcoupled to the RF power amplifier and configured to provide the RF clockto the RF power amplifier.
 9. The power converting system of claim 1,wherein a frequency of the RF clock is an operating frequency of thepower converting system.
 10. The power converting system of claim 1,wherein the controller is configured to: based on the DC voltage,generate the control signal to adjust a phase of the RF clock.
 11. Thepower converting system of claim 10, wherein the RF power amplifierincludes: a phase shifter configured to: receive the control signal fromthe controller, and based on the control signal, adjust the phase of theRF clock.
 12. The power converting system of claim 11, wherein the RFpower amplifier includes: a first switching unit that is configured toreceive the RF clock, a second switching unit that is configured toreceive the RF clock, a third switching unit that is configured toreceive the RF clock through the phase shifter, and a fourth switchingunit that is configured to receive the RF clock through the phaseshifter, wherein the phase shifter is configured to adjust the phase ofthe RF clock and provide the phase adjusted RF clock to the thirdswitching unit and the fourth switching unit.
 13. The power convertingsystem of claim 12, wherein the second switching unit and the thirdswitching unit are coupled to floating ground.
 14. The power convertingsystem of claim 12, wherein the RF power amplifier further includes: aresonant circuit having a first resonant frequency, and wherein anoperating frequency of the RF power amplifier is the same as the firstresonant frequency.
 15. The power converting system of claim 14, whereinthe operating frequency of the RF power amplifier is between 100 kHz and100 MHz.
 16. The power converting system of claim 11, wherein the RFpower amplifier includes: a fifth switching unit that is configured toreceive the RF clock, and a sixth switching unit that is configured toreceive the RF clock, and wherein the phase shifter is configured toadjust the phase of the RF clock and provide the phase adjusted RF clockto the fifth switching unit and the sixth switching unit.
 17. The powerconverting system of claim 16, wherein the fifth switching unit and thesixth switching unit are coupled to floating ground.
 18. The powerconverting system of claim 16, wherein the RF power amplifier furtherincludes: a resonant circuit having a first resonant frequency, andwherein an operating frequency of the RF power amplifier is the same asthe first resonant frequency.
 19. The power converting system of claim18, wherein the operating frequency of the RF power amplifier is between100 kHz and 100 MHz.
 20. The power converting system of claim 1, whereinthe controller is configured to: based on the DC voltage, generate thecontrol signal to adjust a pulse width of the RF clock.
 21. The powerconverting system of claim 20, wherein the RF power amplifier includes:a pulse width controller that is configured to: receive the controlsignal from the controller, and based on the control signal, adjust thepulse width of the RF clock.
 22. The power converting system of claim21, wherein the RF power amplifier includes: a first switching unit thatis configured to receive the RF clock through the pulse widthcontroller, a second switching unit that is configured to receive the RFclock through the pulse width controller, a third switching unit that isconfigured to receive the RF clock through the pulse width controller,and a fourth switching unit that is configured to receive the RF clockthrough the pulse width controller, wherein the pulse width controlleris configured to adjust the pulse width of the RF clock and provide thepulse width-adjusted RF clock to the first switching unit, the secondswitching unit, the third switching unit, and the fourth switching unit.23. The power converting system of claim 22, wherein the secondswitching unit and the third switching unit are coupled to floatingground.
 24. The power converting system of claim 22, wherein the RFpower amplifier further includes: a resonant circuit having a firstresonant frequency, and wherein an operating frequency of the RF poweramplifier is the same as the first resonant frequency.
 25. The powerconverting system of claim 24, wherein the operating frequency of the RFpower amplifier is between 100 kHz and 100 MHz.
 26. The power convertingsystem of claim 21, wherein the RF power amplifier includes: a fifthswitching unit that is configured to receive the RF clock, and a sixthswitching unit that is configured to receive the RF clock, and whereinthe pulse width controller is configured to adjust the pulse width ofthe RF clock and provide the pulse width-adjusted RF clock to the fifthswitching unit and the sixth switching unit.
 27. The power convertingsystem of claim 26, wherein the fifth switching unit and the sixthswitching unit are coupled to floating ground.
 28. The power convertingsystem of claim 26, wherein the RF power amplifier further includes: aresonant circuit having a first resonant frequency, and wherein anoperating frequency of the RF power amplifier is the same as the firstresonant frequency.
 29. The power converting system of claim 28, whereinthe operating frequency of the RF power amplifier is between 100 kHz and100 MHz.
 30. The power converting system of claim 1, wherein therectifier is a Valley Fill rectifier.
 31. The power converting system ofclaim 1, wherein an operating frequency of the RF power amplifier isbetween 13 and 43 MHz.